1. Field of the Invention
The invention relates to an organic light emitting display and manufacturing method thereof.
2. Description of Related Art
An organic light emitting diode (OLED) display is a self emissive display device, which displays images by exciting an emissive organic material to emit light. The OLED display includes an anode (hole injection electrode), a cathode (electron injection electrode), and an organic light emission layer interposed therebetween. When the holes and the electrons are injected into the light emission layer, they recombine to form excitons, which emit light when they transition from an excited state to a ground state.
A plurality of pixels typically comprise an OLED display, each pixel includes an anode, a cathode, and a light emission layer, and are arranged in a matrix. The pixels may be driven in passive matrix (or simple matrix) addressing or active matrix addressing.
A passive matrix type OLED display includes a plurality of anode lines, a plurality of cathode lines intersecting the anode lines and a plurality of pixels, each pixel including a light emission layer. The selection of one of the anode lines and one of the cathode lines cause light emission of the pixel located at the intersection of the selected signal lines.
The active matrix type OLED display includes a plurality of pixels, each including a switching transistor, a driving transistor and a storage capacitor, as well as an anode, a cathode, and a light emission layer. The active matrix type OLED display further includes a plurality of gate lines transmitting gate signals and a plurality of data lines transmitting data voltages. The switching transistor is coupled to one of the gate lines and one of the data lines and transmits the data voltage from the data line in response to the gate signal. The driving transistor receives the data voltage from the switching transistor and drives a current having a magnitude determined depending on the data voltage. The current from the driving transistor enters the light emission layer to cause light emission having intensity depending on the current. The storage capacitor is coupled to the data voltage to maintain the data voltage. The gray scaling of the active matrix type OLED display may be accomplished by controlling the data voltages applied to the driving transistor for adjusting the current driven by the driving transistor. The color representation of the OLED display is obtained by providing red, green and blue light emission layers.
In this active matrix type OLED display, uniform thickness of the light emission layer and large emission area without current leakage are required for high emission quality.
However, the uniformity of the light emission layer thickness is not easily obtained and undesired current leakage near the edges of the light emission layer is often generated.